Method of electrostatically copying information on both sides of an original onto both sides of a support material

ABSTRACT

A method for duplex printing or reproducing the information from both sides of an original document upon a support material by simultaneously forming an electrostatic latent image conforming to each side of the original document on respective photoconductive plates, developing the plates and transferring the developed images from the plates onto opposite sides of the support material.

United States Patent .1191

Punnett 1451" Nov. 27, 1973 [541 METHOD 0F ELECTROSTATICALLY 3,427,6582/1969 Roberts 96/l.3

COPYING INFORMATIQN O T SIDES 3,536,398 10/1970 Bhagat 355/3 OF- ANORIGINAL ONTO BOTH SIDES OF A SUPPORT MATERIAL Frazer D. Punnett,Rochester, NY. Assignee: Xerox Corporation, Rochester, NY.

Filed: Sept. 3, 1971 Appl. 190.; 177,809

Related US. Application Data Division of Ser. No. 751,783, Aug. 12,1968.

Inventor:

U.S. c1.- 96/1 R, 96/13, 117/175,

Int. Cl.....' G03g 13/08, C03g 15/08.

3,580,670 5/1971 Bhagat ...."355 /3 Primary Examiner-William D. MartinAssistant Examiner-M. Sofocleous Attorney-James J. Ralabate et a1.

[5 7] ABSTRACT A method for duplex printing or reproducing the inthesupport material.

2 Claims, 1 Drawing Figure 1 METHOD OF ELECTROSTATICALLY COPYINGINFORMATION ON BOTH SIDES OF AN ORIGINAL'ONTO BOTH SIDES OF A SUPPORTMATERIAL This is a division, of application Ser. No. 751,783,

copy is made of it, then the operator of the copier must reverse thedocument and expose the oposite side to make a copy of it. This two-stepprocedure is very'time consuming and the copier requires the constantattention of the operator so that the document is manipulated properly.In addition, the number of sheets or rolls or paper. used is doubled foreach two-sideddocument reproduced since information can be. convenientlyplaced only on one side of the copy sheet at a time.

Various feeding attachments for copiers have been developed to reversethe two-sided document after copying the first side in order'to make thecopier more completely automatic and eliminatethe need of the manualoperation, but these attachments are usually bulky, expensive tomanufacture andsubject to maladjustment thereby creating the hazard of"possible destruction of the original document as it is guided by themechanism. Suchattachments, although they can be made to operaterapidly, do not ove'rcomethe disadvantage of successive exposures ofeach side .of the original document. which wastes time, or thedisadvantage of using two sheets for a complete copy of the twosidedoriginal-document which wastes materials.

Although most copiers have the capability of reproducing-information onthe two sides of a single copy sheet if each side of the copy sheet isexposed, 'developed and fixed individually, it is not an easyresult toaccomplish,,The copy sheet must be redirected into the charge andtransfer the images to opposite sides of a support material.

Another object of the invention is to transfer in sub stantial alignmentonto opposite sides of a support material the developed images on twoxerographic plates.

This invention uses two photoconductive plates upon which electrostaticlatent images can be produced. The

latent images are produced on the plates simulta neously, developed withtoner particles or powder and then transferred to a final supportmaterial. In one embodiment of the invention two photosensitive beltsare used in copying both sides of a two-sided original document. Bothbelts travel at idential surface speed while an optical patternconforming to one side of the original document is produced to exposethejfirst belt and an optical pattern conforming to the second side ofthe original document is produced to expose the second belt. Aftertheimages are developed with toner particles, they are transferred from thebelts to opposite sides of the support material. I v

For a better understanding ofthe invention as well as otherobjects andfurther features thereof, reference is had to the following detaileddescription of the'inven tion to be used in conjunction with theaccompanying drawing, which shows a schematic arrangement of a xeshapesuch as aflat plate, drum, endless belt or any continuous web or otherform of material bearing inforfeed tray of the machine after the firstside'of the original document has been copied onto it and madepermanent. Then, after the copy sheet is reversed and fed back into themachine, the second side of the original document is exposed, developedand fixed to it. Even under ordinary conditions the reventry of thecopy, sheet to the copier is difficult especially when :many originaldocuments are copied in succession since the correct original documentas well as the proper side of the original document must be exposed uponany specific sheet in order that the two sides of the copy sheet matchthe two sides of the original document.

Accordingly, it is an object of this invention to improve the method andapparatus for copying both sides of an original document which overcomesthe deficiencies of the prior art devices as described above.

A second object of the invention is to :form images on both sides of asupport material in a continuous process.

mation on both sides. It may also comprise. two sheets or webs printedin simplex, that is, printed only on one side and positionedback-to-back to form two sided printed material. Simultaneously, opticalpatterns conforming to each side of the original are produced to exposerespectively a plate and thereafter, both plates are developed and thedeveloped images transferred onto I opposite sides of support materialsuch as sheet material or web. An original bearing information to bereproduced on both sides; e.g., sheet 46, is placed be tween twoplatens, right platen 47 and left platen 48, where it is held in aflatened, unbuckled position while illumination thereof by any suitablemeans is taking place. 'lf-the original takes the form of a sheet it canbe placed and held between the platens either manually or by anautomatic document feeding mechanism .until exposure is completed. If,in the alternative, the original takes the form of a continuous web,itcan be fed between the two platens in acontinuous manner and heldrelative to theplates by any suitable means. The illumination lamps 101,102 may be arranged to scan each side of the original 46, such as theillumination apparatus disclosed in U. S. PatrNo. 3,062,095 or beadapted to effect flash exposure of the original. It is intended,

that the scanning operation be such that the information on each side ofthe original be scanned, projected and imaged onto the respectivephotoconductor belts 59,66in synchronism with the movement of thesurface of the belts. The two sides of the document 46 are illuminatedsimultaneously during exposure to keep the time for duplex exposure at aminimum and to assure that both images eventually transferred to recordmate rial or web 71 are placed on opposite sides thereof in. substantialalignment. 7

The optical patterns to'which plates 66 and 59 are exposed can begenerated by any other devices. For instance, each of the opticalpatterns could be generated by illuminating a moving transparency whichmoves in synchronism with the belt surface or by a flash exposure aspreviously stated. If the plates59,66 are in the form of xerographicdrum, the imaging must be accom plished by scanning. In addition, themeans of generating an optical pattern to be exposed onto one of thephotoconductor belts may be different from the means for generating anoptical pattern to be exposed onto the other belt. i I g 7 As mentionedabove, the document to be copied by the apparatus shownin the drawing isin the form of sheet 46 bearing information on both of its surfaces. Thesheet is held between platens 47 and 48 while each side is scanned bydevices 101 and 102. Imaging'light,

rays of information on the left sideof the sheet is directedto a mirror91 which, in turn, reflects them onto mirror 92. This combination of themirrors directs the light rays through lens 54 which focuses theresultant image on plate 59. In a similar manner imaging light rays ofthe information on the right'side of sheet 46 is directed to a' mirror93 which, in turn, reflects them onto mirror 94. This combination ofmirrors 93 and 94 directs the light rays through lens 53 which focusesthe resultant image on plate 66. The above-described lensmirror systemis intended only as an example of an optical system which canbe used toexpose plates 59 and 66 to the optical patterns generated by anillumination device and sheet 46, and any suitable system that can placean optical image of the one shown. I

The plates 59 and 66 are electrostatic plates which are capable ofretaining an electrostatic latent image in response to the optical lightpattern which falls upon them. In order to assure that such a latentimage is fully retained on each plate, each plate is exposed to itsrespective optical pattern in a darkened area. Prior to the right sideof sheet 46 being illuminated to expose onto plate 66, thephotosensitive layer of the plate is charged uniformly by a coronacharging device 62, and after exposure, the plate is developed by asuitable developing device schematically indicated by 64. The platethereafter locates the developed image at a position where it makescontact with the right side of web or record material 71 where transferdevice 63 aids in the transfer of the developed image to the web. Afterthe image has been transferred from the plate 66, cleaning device 68removes any residual developer powder remaining on the surface of theplate thereby preparing the drum for reuse. Further description ofxerographic processing and of details of the devices 62, 63, 64 and 68,the power supplies and drives therefor are not necessary to understandthe invention herein. Such details may be acquired from any one ofanumber of U. S. patents, such as U. S. Pat. No. 3,162,109 to Mayo et al.

In a similarmanner, the electrostatic plate 59 prior to exposure isfirst uniformly charged by any suitable device, such as corona chargingdevice 51, and thereafter exposed to a light pattern or image conformingto passes the cleaning device 52 which removes any residon the platescan be used in lieu Transfer devices 62 and 72 are shown as coronagenerating devices similar to those disclosed in Schaffert U.S. Pat. No.2,576,047. They comprise either a unitary or a plurality ofwiresconnected to a high voltage source. The wire is supported in aconductive shield that is arranged in closely spaced relation to thesurface to be charged; i.e., web 71. When the wire is'energized, coronais generated'along the surface of the wire and ions of the necessarypolarity are caused to be deposited on the web surface. In addition to acorona device, transfer can be accomplished by any suitable method. Forexample, a roller, either heated or unheated, can be placed adjacent theweb on the side of the web opposite theplate in order to accomplishtransfer by compression or heat and compression.

The web 71 can be any support substrate material to which the image canbe fused or otherwise made permanent. Web 71 may also comprise anysuitable material which serves as an intermediate to which the developedimage is transferred prior to being placed on its final supportmaterial. For instance, the web can be pa.- per, plastic, metal, etc andcan take the form of individual 'she'ets,'a continuous strip, or anyother convenient formgln the'drawing the web 71 is a continuous strip ofpaper fed froma supply roll 69 at the sameilineal speed as the speed ofthe belts.

The web is initially fed from the roll 69, and, after the transfer andfusing steps have taken place for the images on'both sides'of the web,it is rewound on a takeup roll 79. The web is first passed adjacentplate 59 where the image on the surface of the plate is transferred tothe left side of the web. After this transfer step, the web can be movedunder a fuser (not shown) v which acts to partially fuse the transferredimage upon the web.

The image may be partially fused at this point, but

there must be assurance that the web is sufficiently cool so as not toadversely affect the transfer process to its other side. Although it maybe advantageous that some fusing take place on the image firsttransferred before an image is tranferred to the opposite side in orderto revent distortion or smearing of the image first transfered, suchfusing is optional. The image transferred onto the left side of thewebfrom plate 59 may also be completely fused by such an element alongthe path of the web between transfer devices 62'and 72. However, becauseof the quantity of heat necessary to effect good fusing, the web wouldeither have to be quickly cooled before the image on drum 66 weretransferred to the opposite side of the web or the path of travelbetween the fuser and corona transfer device 62 would have to belengthened in order that sufficient time is given for the surroundingair to cool the web before transfer.

I It is preferred that all fusing take place after both images have beentransferred to the web 71 from their respective plates. Radiant heatfusing devices 82 and 83 make permanent the images placed on the leftand right sides of the web as the web 5 passes between them.

Whether the fusing of thetwo developer powder imwhich issubstantiallythe speed of the web, to assure transfer of the images tothe web without smearing, and because the belts are exposed to theirrespective optical patterns simultaneously, is necessary to make someaccommodation for getting the two images transferred to the web oppositeone another. As can be seen in the'drawing,the distance that the plate59. travels between its exposure station l0l'and its transfer station102 is shorter than jthe'distance that plate 66 travels between itsexposure station 103 and its tranfer station 104. The difference inthese two distances is equivalent 7 to the distance the web travelsbetween the transfer stations 102 and 104 and, therefore, the imageexistent on plate 66 is transferred, with the aid of transfer device 62onto the right side of the web in substantial alignment with the imagetranferred onto the left side of the web. Likewise, the period of timewhich elapses be-- tween the time the image on plate 59 commencestransfer to the web and the time the image on plate 66 commencestransfer to the web is a function of the time the web takes to travelbetween transfer device 72 and transver device62.

The invention herein is disclosed in detail within the environment ofthe xerographic process. It will be appreciated, however, that thexerographic reproduction 1 process is not critical to the invention. Anysuitable manner of forming a powder image on plates 59 and 66 which canbe transferred to a record material can be utilized and methods otherthan xerography maybe used to form the images on the plates such as bythe utilization of character electrodes as disclosed by Shull in ableduplex copy of the document 46, the printing process may involve thephotoconductor zinc oxide paper in place of the photoreceptors 59, 66.In this arrangement, each of the zinc oxide photo-receptor may be in theform of cut sheets or web. 2

It is intended that appropriate drive mechanisms and control circuits bea part of the gneeral disclosure herein, but such apparatus are notshown since the elements can be of any suitable design to accomplish theoperational movement of the invention, as described above.

What is claimed'is:

l. The method of printing the information on two sides of an originalincluding the steps of forming a first electrostatic latent image on aphotoreceptor surface of the information onone side of otherphotoreceptor surface of theinformation on the other side of theoriginal simultaneously with the formation of said first latent image,

and developing the two latent images on their respective photoreceptorsurfaces with finely divided electrostatic particles thereby forming onthe surfaces respectively, visible images of the information on eachside of the original.

2. The method of printing the information on two sides of an originalrespectively onto two sides of support material includingthe steps offorming a first electrostatic latent image on a photoconductive surfaceof the information on one side of the original, r

developing the first latent image and transferring the developed imageonto one side'of the support material,

support material.

forminga second electrostatic latent image on an

2. The method of printing the information on two sides of an originalrespectively onto two sides of support material including the steps offorming a first electrostatic latent image on a photoconductive surfaceof the information on one side of the original, developing the firstlatent image and transferring the developed image onto one side of thesupport material, forming a second electrostatic latent image on anotherphotoconductive surface of the information on the other side of theoriginal simultaneously with the formation on said first latent image,and developing the second latent image and transferring the developedimage onto the other side of the support material.